Watts-per-candle photometer.



H. E. IVES. WATTS-PER-CANDLE PHOTOMETER. APPLICATION FILED MAR. 10, 1913.

1,100,883. Patented June 23, 1914,

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w/messss: INVENTOR figrberf 5/)66 v (is Anvk/ven UNITED STATES PATENT OFFICE HEBBEBT' H. IVES, or MOUNT AIRY', PENNS YLVANfA, nssrenon, TO THE UNITED GAs' IMPROVEMENT couP'ANY, or PHILADELPHIA, mamsrnvmgm, A CORPORATION OF PENNSYLVANIA.

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Specification of Letters Patent.

Patented June 23, 1914'.

To all whom it may concern:

Be it known that I Hammers E. Ives, a

citizen of the United States, residing at Mount Airy, in the county of Philadelphia and State of: Pennsylvaniahave invented a certain new and useful Watts-Per-Candle Photometer, of which the following is a specification.

The principal object of the present invention is to provide an instrument for finding the voltage at which incandescent electric lamps will give their standard efficiency or watts-per-candle power, and to make it as simple in operation, as the single circuit candle power volt scale photometer heretofore used, and, like it, operable on an unsteady voltage supply.

I accomplish the above object by applying two principles :-'I-he first principle is that of registerlng both rate of energy consumption and candle power'by' the same indication, namely, illumination; and the second principle is that of measuring the test lamp rate of energy consumption relatively in terms of the standard or comparison lamp rate of energy consumption. 7

The invention will be claimed at the end hereof, but will be first described in connection with the embodiment selected from other embodiments for illustration in the accompanying drawings, in which- Figure 1, is an elevational view, partly in section and diagrammatically illustrating. a wattser-candle photometer for use on one sing e circuit wiring and embodying features of the invention, and, Fig. 2, is a side elevation of a detail.

In the drawings 1, is a photometer head com rising a photometric screen 2, both sides of w ich may be viewed in juxta-position b suitable optical means not shown but whic are well understood. At a short distance in front of each side of this screen 2 is a translucent diffusing glass 3 and 4, over which is an opaque plate 5, aperture. The light from the test lamp 7 and the light from the comparison lam are incident upon the apertures which t en serve as secondary light sources. This is indicated by the arrows in Fig. 1.

9 an 19 are instruments for measuring the rate oi energy consumption. They are shown as ammeters since a response to current is suflicient, because the voltage is conerforated at 6 by an sta-nt or varies similarly at both, as will be more" fiully explained; Each" ammeter carries an opaque sector or screen 11 upon its indicating or movable needle 12 in such manner that the aperture beneath is opened an amount corresponding to the current passing through that ammeter. Each am meter is connected in series with the lamp which illuminates the side of the hotometer opposite to the side over whic its attached sector or screen moves. From the source 13 there is a lead 14 and also a lead 15. From the lead 14 the current divides, one branch 16, passing through the test lamp 7 and then through the ammeter to the lead 15; the other branch 17 passing through the comparison lamp 8, then through the amineter9 and to the lead 15; thus the lamps 7 and 8 are in parallel and the ammeter 9 is in series with the lamp 8 and theammeter 10 is in series with the lamp 7. By these means the two sides of the photometric screen 2 receive illuminations respectively proportional to the current (Watts, since.

voltage constant or varies similarl at both lamps) and to-the candle power 0 the test; source; The position of photometric balance corre ontls to' definite ratio of current; (watts to candle" power and all lampsllrought to balance onthesame point have the same efliciency. All other points on the scale 18 correspond to definite other ,efiiciencies or to voltage requirements.

the use of two ammeters, as-desoribed-', .the illumination which represents the current in the test source is made to correspond to the relative value of the current as measured in terms of the standard or comparison lamp current, whereby the efiects of line voltage fluctuations are equally present on each side and so become negligible; it being understood that lamps of similar filament composition or characteristics are used at 7 and 8.

The mode of operation of the described instrument may be explained as follows and for the sake of this description it will be assumed that at first a test lamp is used which is equal in efliciency and candle power to the comparison lamp at the voltage obtaining on the circuit at the time of the test, and that both lamps are equal] distant from the glasses 3 and 4. Evi ently the screens 11 will so uncover the apertures 6 that there is a photometric balance on the screen 2. If now a test lamp be used whi h i equal in efliciency with the comparison lamp, but of greater or less candle power, such test lamp will require more or less current than did the test lamp referred to in the first instance. In consequence of this the 'ammeter 10 will shift its screen, thus increasing or diminishing the light that falls from the comparison lamp 8 and consequently increasing or decreasing the illumination from the secondary source 4 upon the screen preserving in this way the photometric match and showing that the test and comparison lamps are of equal elficiency at the same voltage. If now a test lamp of greater or less efficiency than the comparison lamp be used, the photometric match will no longer exist and in order to obtain a photometric match the test lamp 7 will have to be moved toward or away from the screen 2, or in other words, along the bar 19 and when the match is obtained the scale 18 indicates efliciency or upon a properly calculated scale the voltage at which the test lamp must be run in order to obtain the same eflieiency as that of the comparison lamp. In the last instance the photometric match is dependent upon the coaction of the ammeters 9 and 10, which respond to current, (watts, voltage being the same on each side), and on the osition of the test lamp 7 on the bar, whlch is representative of candle power, so that it is really dependent upon the watts-per-candle power.

It will be obvious to those skilled in the art to which the invention relates that modifications may be made in details of construction and arrangement, hence the in vention is not limited in that regard or in any way further than the prior state of the art may require, but

Having thus described the nature and objects of the invention, what I claim as new and desire to secure by Letters Patent is:

1. A watts-per-candle photometer comprising the combination of a photometric screen, devices responsive to rate of energy consumption and arranged to transmit to the two sides of the screen fractions of the light from test and comparison sources, each proportional to the rate of energy consumption of the source illuminating the opposite side of the screen.

2. A watts-per-candlephotometer comprising the combination of test and comparison lamps in parallel relation, a photometric screen, secondary sources of illumination respectively illuminated b the lamps and arranged on opposite sides 0 the screen, devices responsive to current and respectively in series relation with each lamp and each adapted to control the illumination of the secondary source illuminated by the I other lamp, and a scale for indicating the relative positions of the lamps and secondary sources of illumination, substantially as described.

3. A watts-pencandle photometer comprising the combination of test and comparison lamps in parallel relation, a photometric screen, devices responsive to rate of energy consumption and respectively in series relation with each lamp and adapted 3 to control the illumination, by the other lamp, and a photometric scale, substantially as described.

In testimony whereof I have hereunto signed my name.

HERBERT E. IVES.

Witnesses:

Cmrromy K. Cassrm, FRANK E. FRENCH. and 8. 

